Lubricant composition

ABSTRACT

A lubricating oil composition used in an internal combustion engine is provided. The internal combusting engine uses a fuel that contains at least one fat and oil selected from a group consisting of natural fat and oil, hydrotreated natural fat and oil, transesterified natural fat, and oil and hydrotreated transesterified natural fat and oil. The lubricating oil composition includes: base oil of lubricating oil; a component (A) containing a boron derivative of an alkyl or alkenyl-substituted succinimide compound having a number average molecular weight of 200 to 5000; and a component (B) containing an alkaline earth metal-based detergent. The component (A) is contained by 0.01 to 0.2 mass % in terms of boron of a total amount of the composition while the component (B) is contained by 0.35 mass % or less in terms of the alkaline earth metal of the total amount of the composition.

TECHNICAL FIELD

The present invention relates to a lubricant oil composition to be usedin an internal combustion engine that uses a fuel originating fromnatural fat and oil.

BACKGROUND ART

These days, environmental regulations are being increasingly tightenedon a global scale, among which fuel efficiency regulations and exhaustemission regulations for automobiles are especially being furthertightened. Demands for tightening of the regulations are derived fromenvironmental issues such as global warming and resource conservationdue to a concern for depletion of petroleum resources.

Meanwhile, plants living on the earth absorb carbon dioxide in the air,water and sunlight to photosynthetically generate carbohydrate andoxygen. What is called, biofuel, which is manufactured from plant-basedplant oil, has been gathering remarkable attentions because of itseffects on reduction of carbon dioxide (a main cause of global warming)and reduction of atmospheric contaminants emitted from automobiles. Inline with an idea of carbon neutral advocating that carbon dioxidegenerated due to combustion of plant biomass is not counted as acontributor to an increase of the global warming gas, ratio at which thebiofuel is mixed in hydrocarbon fuel is expected to be increased in thefuture (cf. Non-Patent Document 1:).

Non-Patent Document 1: Koji YAMANE, From Biodiesel Deep Fryer to FuelTank, (Tokyo-Tosho-Shuppankai, May of 2006)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An important problem in an internal combustion engine, especially in adiesel engine, has been how to reduce environment pollution caused bysuch emission gas components as particulate matters (PM such as soot)and NO_(x). An effective solution is to mount such an exhaust purifyingdevice as a diesel particulate filter (DPF) or an exhaust purifyingcatalyst (oxidization or reduction catalyst) on an automobile. Forexample, soot generated in the diesel engine adheres to the DPF to beremoved by oxidization and combustion.

When the DPF is mounted on the diesel engine, post-injection of fuel isgenerally conducted so as to combust the soot accumulated on the filter.Engine oil is diluted by the fuel due to the post-injection, so thatperformance of the engine oil is expected to be deteriorated.Particularly, since biofuel can be easily accumulated in the engine oildue to its property and generates polar compounds when degraded anddecomposed, the biofuel may adversely affect detergency of engine partssuch as a piston. Such a defective phenomenon greatly depends onproperties of lubricating oil used in the internal combustion engine.

An object of the present invention is to provide a lubricating oilcomposition that is excellent in lubricity and engine-parts detergencyeven when biofuel or fuel mixed with the biofuel is employed in aninternal combustion engine such as a diesel engine, and that imposesless adverse effects on the environment.

Means for Solving the Problems

In order to solve the above-mentioned problems, according to an aspectof the present invention, lubricating oil compositions as follows areprovided:

(1) a lubricating oil composition used in an internal combustion engine,the internal combustion engine using a fuel that contains at least onefat and oil selected from a group consisting of natural fat and oil,hydrotreated natural fat and oil, transesterified natural fat and oiland hydrotreated transesterified natural fat and oil, the lubricatingoil composition containing: base oil of lubricating oil; a component (A)containing a boron derivative of a succinimide compound substituted byan alkyl or alkenyl group having a number average molecular weight of200 to 5000; and a component (B) containing an alkaline earthmetal-based detergent, in which the component (A) is contained by 0.01to 0.2 mass % in terms of boron of a total amount of the compositionwhile the component (B) is contained by 0.35 mass % or less in terms ofthe alkaline earth metal of the total amount of the composition;(2) the above-described lubrication oil composition, in which a massratio (B/N) of boron (B) and nitrogen (N) contained in the component (A)is 0.5 or more;(3) the above-described lubrication oil composition, in which aphenol-based antioxidant and/or an amine-based antioxidant are containedby 0.3 mass % or more of the total amount of the composition;(4) the above-described lubrication oil composition, in which a sulfurcontent is 0.5 mass % or less of the total amount of the composition;(5) the above-described lubrication oil composition, in which aphosphorus content is 0.12 mass % or less of the total amount of thecomposition; and(6) the above-described lubrication oil composition, in which a sulfatedash content is 1.1 mass % or less.

The lubricating oil composition according to the aspect of the presentinvention exhibits excellent detergency for engine parts such as apiston in the internal combustion engine using what is called biofuelmade of natural fat and oil and the like even when the biofuel is mixedinto the engine oil. Especially, the lubricating oil is excellent inhigh-temperature detergency when the engine reaches a high temperature.Even when used in a diesel engine with a DPF, the lubricating oilcomposition can reduce residual ash content on the DPF, therebypreventing performance of the DPF from being deteriorated.

Natural fat and oil used in the present invention is not limited toplant-derived fat and oil but may include animal-derived fat and oil.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described in detailbelow.

A lubricating oil composition according to the present invention is usedin an internal combustion engine, the internal combustion engine using afuel that contains at least one fat and oil selected from a groupconsisting of natural fat and oil, hydrotreated natural fat and oil,transesterified natural fat and oil and hydrotreated transesterifiednatural fat and oil.

Although the natural fat and oil may be a variety of animal-derived orplant-derived fat and oil that is generally available in nature, thenatural fat and oil is preferably plant oil that contains ester of fattyacid and glycerin as a major ingredient, examples of which are saffloweroil, soybean oil, canola oil, palm oil, palm kernel oil, cotton oil,coconut oil, rice bran oil, benne oil, castor oil, linseed oil, oliveoil, wood oil, camellia oil, earthnut oil, kapok oil, cacao oil, hazewax, sunflower seed oil, corn oil and the like.

The hydrotreated natural fat and oil is formed by hydrogenating theabove fat and oil under the presence of a suitable hydrogenatingcatalyst.

The hydrogenating catalyst is exemplified by a nickel-based catalyst, aplatinum family (Pt, Pd, Rh, Ru) catalyst, a cobalt-based catalyst, achrome-oxide based catalyst, a copper-based catalyst, an osmium-basedcatalyst, an iridium-based catalyst, a molybdenum-based catalyst and thelike. A combination of two or more of the catalysts may also bepreferably used as the hydrogenating catalyst.

The transesterified natural fat and oil is ester formed bytransesterifying triglyceride contained in the natural fat and oil underthe presence of a suitable ester-synthesis catalyst. For instance, bytransesterifying lower alcohol and the fat and oil under the presence ofthe ester-synthesis catalyst, fatty acid ester usable as biofuel ismanufactured. The lower alcohol, which is used as an esterifying agent,is exemplified by alcohol having 5 or less carbon atoms such asmethanol, ethanol, propanol, butanol, pentanol and the like. In view ofreactivity and cost, methanol is preferable. The lower alcohol isgenerally used in an amount equivalent to the fat and oil or more.

The hydrotreated transesterified natural fat and oil is formed byhydrogenating the above transesterified fat and oil under the presenceof a suitable hydrogenating catalyst.

The natural fat and oil, the hydrotreated natural fat and oil, thetransesterified natural fat and oil, and the hydrotreatedtransesterified natural fat and oil can be preferably used as mixed fuelby adding the above to fuel formed of hydrocarbon such as light oil.

The lubricating base oil used in the lubricating oil compositionaccording to the present invention is not particularly limited but maybe suitably selected from any mineral oil and synthetic oil that havebeen conventionally used as base oil of the lubricating oil for theinternal combustion engine.

Examples of the mineral oil are mineral oil refined by processinglubricating oil fractions by at least one of solvent-deasphalting,solvent-extracting, hydrocracking, solvent-dewaxing, catalytic-dewaxingand hydrorefining (the lubricating oil fractions are obtained byvacuum-distilling atmospheric residual oil obtained by atmosphericallydistilling crude oil) and mineral oil manufactured by isomerizing waxand GTL WAX.

On the other hand, examples of the synthetic oil are polybutene,polyolefin (α-olefin homopolymer or copolymer such as ethylene-α-olefincopolymer), various esters (such as polyol ester, diacid ester andphosphoric ester), various ethers (such as polyphenylether), polyglycol,alkylbenzene, alkyl naphthalene and the like. Among the above,polyolefin and polyol ester are particularly preferable.

In the present invention, one of the above mineral oil may be singularlyused or a combination of two or more thereof may be used as the baseoil. In addition, one of the above synthetic oil may be singularly usedor a combination of two or more thereof may be used. Further, acombination of at least one of the above mineral oil and at least one ofthe above synthetic oil may be used.

Although viscosity of the base oil subjects to no specific limitationand varies depending on usage of the lubricating oil composition,kinematic viscosity thereof at 100 degrees C. is generally preferably 2to 30 mm²/s, more preferably 3 to 15 mm²/s, much more preferably 4 to 10mm²/s. When the kinematic viscosity at 100 degrees C. is 2 mm²/s ormore, evaporation loss is small. When the kinematic viscosity at 100degrees C. is 30 mm²/s or less, power loss due to viscosity resistanceis restricted, thereby improving fuel efficiency.

As the base oil, oil whose % CA measured by a ring analysis is 3 or lessand whose sulfur content is 50 ppm by mass or less can be preferablyused. The % CA measured by the ring analysis means a proportion(percentage) of aromatic content calculated by the n-d-M method (a ringanalysis). The sulfur content is measured based on Japanese IndustrialStandard (hereinafter called, JIS) K 2541.

The base oil whose % CA is 3 or less and whose sulfur content is 50 ppmby mass or less exhibits a favorable oxidation stability. Such base oilcan restrict an increase of acid number and a generation of sludge,thereby providing a lubricating oil composition that is less corrosiveto metal. The sulfur content is more preferably 30 ppm by mass or less.The % CA is more preferably 1 or less, much more preferably 0.5 or less.

In addition, viscosity index of the base oil is preferably 70 or more,more preferably 100 or more, much more preferably 120 or more. In thebase oil whose viscosity index is 70 or more, a viscosity change due toa temperature change is small.

The component (A) of the lubricating oil composition according to thepresent invention is a boron derivative of a succinimide compoundsubstituted by an alkyl or alkenyl group having a number averagemolecular weight of 200 to 5000.

Such a boron derivative of the succinimide compound can be obtained byexemplarily reacting (a) a succinic acid substituted by an alkyl oralkenyl group having the number average molecular weight of 200 to 5000or an anhydride of the succinic acid, (b) polyalkylene polyamine and (c)a boron compound.

Materials (a), (b) and (c) and synthetic methods therefor will bedescribed below.

As the material (a), the succinic acid substituted by the alkyl oralkenyl group or an anhydride of the succinic acid is used. The numberaverage molecular weight (hereinafter may be abbreviated as molecularweight or Mn) of the alkyl or alkenyl group is typically 200 to 5000,preferably 500 to 2000. When the molecular weight of the alkyl oralkenyl group is less than 200, the eventually-obtained boron derivativeof the succinimide compound may not be sufficiently dissolved in thebase oil of the lubricating oil. When the molecular weight is more than5000, the succinimide compound may become so highly viscous as to impairthe usability.

As the alkyl or alkenyl group having such a molecular weight, a polymeror a copolymer of monoolefin and diolefin having 2 to 16 carbon atoms ora hydride of the polymer or the copolymer is typically used. Examples ofmonoolefin are ethylene, propylene, butene, butadiene, decene, dodecene,hexadecene and the like. Among the above-listed monoolefin, butene isparticularly preferable in the present invention because of its enhancedhigh-temperature detergency for the engine parts and its availability. Apolybutenyl group (a polymer of the butene) and a hydrogenatedpolybutenyl group (an alkyl group obtained by hydrogenating thepolybutenyl group) are more preferable.

The alkyl or alkenyl substituted succinic acid or an anhydride of thesuccinic acid as the material (a) may be obtained by reacting asubstance such as polybutene having the molecular weight equivalent tothat of the alkyl or alkenyl group with a substance such as maleicanhydride by a conventional method.

Although polyalkylene polyamine is used for the material (b), 5 mol % ormore of the total material is preferably formed from polyalkylenepolyamine having a terminal ring structure. The entirety of the material(b) may be formed from polyalkylene polyamine having a terminal ringstructure, or the material may be a mixture of polyalkylene polyaminehaving a terminal ring structure and polyalkylene polyamine having noterminal ring structure. When polyalkylene polyamine having a terminalring structure is contained by 5 mol % or more, engine-parts detergencyis further improved, which is an object of the present invention. Whenthe content of the polyalkylene polyamine is 10 mol % or more, further20 mol % or more, the detergency is further improved, especiallydetergency at a high temperature is enhanced.

In the present invention, the upper limit on the content of polyalkylenepolyamine having a terminal ring structure is preferably 95 mol % orless, more preferably 90 mol % or less. When the content exceeds 95 mol%, the manufactured boronated succinimide compound may become so highlyviscous as to impair manufacturing efficiency of the compound andsolubility of the product in the base oil of the lubricating oil may bedeteriorated. Accordingly, the content of polyalkylene polyamine havinga terminal ring structure is preferably 5 to 95 mol %, more preferably10 to 90 mol %.

The terminal ring structure of polyalkylene polyamine having a terminalring structure is preferably represented by a formula (1) as follows.

In the formula (1), p and q each represent an integer in a range of 2 to4. Particularly, a group where both p and q are 2, i.e., piperazinylgroup is preferable. A representative example of polyalkylene polyaminehaving a terminal ring structure is aminoalkyl piperazine having aterminal piperazinyl structure such as aminoethyl piperazine,aminopropyl piperazine, aminobutyl piperazine, amino(diethylenediamino)piperazine, amino(dipropyldiamino) piperazine and the like. Among theabove, aminoethyl piperazine is particularly preferable in view of itsavailability.

On the other hand, polyalkylene polyamine having no terminal ringstructure means polyalkylene polyamine having no ring structure orpolyalkylene polyamine having a non-terminal ring structure.Representative examples of polyalkylene polyamine having no ringstructure are polyethylene polyamines such as ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine andpentaethylenehexamine, propylenediamine, dibutylenetriamine,tributylenetriamine and the like. A representative example ofpolyalkylene polyamine having non-terminal ring structure isdi(aminoalkyl)piperazine such as di(aminoethyl)piperazine.

A mixture of polyalkylene polyamine and polyethylene polyamine such astriethylenetetramine, tetraethylenepentamine and pentaethylenehexamineamong the above listed polyalkylene polyamine that may have a ringstructure is particularly preferable because of its enhancedhigh-temperature detergency for engine-parts and its availability.

As the material (c), a boron compound is used. Examples of the boroncompound are boracic acid, boric anhydride, borate ester, boric oxideand boron halogenide. Among the above, boracic acid is particularlypreferable.

The component (A) according to the present invention can be obtained byreacting the materials (a), (b) and (c). Without special limitations,any known methods of reacting can be used. For instance, by reacting thematerials by the following manner, the target substance can be obtained.The materials (a) and (b) are initially reacted with each other, thenits reaction product is reacted with the material (c). A mixing ratio ofthe materials (a) to (b) in the reaction of the material (a) and (b) ispreferably 0.1-to-10 to 1 (mole ratio), more preferably 0.5-to-2 to 1(mole ratio). A reaction temperature of the materials (a) and (b) ispreferably in a range of approximately 80 to 250 degrees C., morepreferably in a range of approximately 100 to 200 degrees C. At the timeof reacting, depending on the materials, or in order to adjust thereaction, solvents such as an organic solvent exemplified by hydrocarbonoil may be used as necessary.

Subsequently, the thus-obtained reaction product of the materials (a)and (b) is reacted with the material (c). A mixing ratio of polyalkylenepolyamine to the boron compound as the reaction material (c) istypically 1 to 0.05-to-10, preferably 1 to 0.5-to-5 (mole ratio). Areaction temperature therefor is typically approximately 50 to 250degrees C., preferably 100 to 200 degrees C. At the time of reacting, asin the reaction of the materials (a) and (b), depending on the materialsor in order to adjust the reaction, solvents such as an organic solventexemplified by hydrocarbon oil may be used as necessary.

As a product of the above reaction, a boron derivative of a succinimidecompound substituted by an alkyl or alkenyl group having a numberaverage molecular weight of 200 to 5000 (the (A) component) is obtained.In the present invention, one of the component (A) may be singularlyused or a combination of two or more thereof may be used.

The content of the component (A) in the lubricating oil compositionaccording to the present invention is 0.01 to 0.2 mass % in terms ofboron (atoms) of the total amount of the composition, preferably 0.01 to0.15 mass %, more preferably 0.01 to 0.1 mass %. Since a predeterminedamount or more of boron is contained in the component (A), even whenbiofuel is mixed into the lubricating oil composition, pistons can befavorably cleaned in the high-temperature internal combustion engine.When the content of boron is less than 0.01 mass %, sufficienthigh-temperature detergency is not obtained. When the content of boronexceeds 0.2 mass %, no further improvement is made on thehigh-temperature detergency, which is of little practical use.

A mass ratio (B/N) of boron (B) and nitrogen (N) contained in thecomponent (A) is preferably 0.5 or more, more preferably 0.6 or more,much more preferably 0.8 or more. When B/N is 0.5 or more,high-temperature detergency for engine parts is greatly enhanced.

Although a boronated succinimide-based compound can be obtained byinitially reacting the materials (a) and (b) and subsequently reactingthe reaction product thereof with the material (c), the reaction ordermay be changed such that the materials (a) and (c) are initially reactedand the reaction product thereof is subsequently reacted with thematerial (b). With this reaction order, the target boronated succinimidecompound may also be likewise obtained.

The component (B) of the lubricating oil composition according to thepresent invention is an alkaline earth metal-based detergent. Forexample, one selected from a group consisting of alkaline earth metalsulfonate, alkaline earth metal phenate and alkaline earth metalsalicylate and a mixture of two or more selected from the group may bepreferably used.

An example of alkaline earth metal sulfonate is alkaline earth metalsalt of alkyl aromatic sulfonic acid obtained by sulfonating an alkylaromatic compound having a molecular weight of 300 to 1500 (preferably400 to 700). The alkaline earth metal salt is exemplified by magnesiumsalt and/or calcium salt and the like, among which calcium salt ispreferably used.

An example of alkaline earth metal phenate is alkaline earth metal saltof alkylphenol, alkylphenol sulfide and a Mannich reaction product ofalkylphenol. The alkaline earth metal salt is exemplified by magnesiumsalt and/or calcium salt and the like, among which calcium salt ispreferably used.

An example of alkaline earth metal salicylate is alkaline earth metalsalt of alkyl salicylic acid. The alkaline earth metal salt isexemplified by magnesium salt and/or calcium salt and the like, amongwhich calcium salt is preferably used. An alkyl group forming thealkaline earth metal-based detergent preferably has 4 to 30 carbonatoms. The alkyl group is more preferably a linear or branched alkylgroup having 6 to 18 carbon atoms, in which 6 to 18 carbon atoms may bein a linear chain or in a branched chain. The alkyl group may be aprimary alkyl group, a secondary alkyl group or a tertiary alkyl group.

In addition, alkaline earth metal sulfonate, alkaline earth metalphenate and alkaline earth metal salicylate may be neutral alkalineearth metal sulfonate, neutral alkaline earth metal phenate and neutralalkaline earth metal salicylate obtained by: directly reacting theabove-described alkyl aromatic sulfonic acid, alkylphenol, alkylphenolsulfide, a Mannich reaction product of alkylphenol, alkyl salicylic acidor the like with alkaline earth metal base exemplified by an oxide or ahydroxide of alkaline earth metal such as magnesium and/or calcium; orconverting the above-described substance into alkali metal salt such assodium salt or potassium salt and subsequently substituting the alkalimetal salt with alkaline earth metal salt. Alternatively, alkaline earthmetal sulfonate, alkaline earth metal phenate and alkaline earth metalsalicylate may be: basic alkaline earth metal sulfonate, basic alkalineearth metal phenate and basic alkaline earth metal salicylate obtainedby heating neutral alkaline earth metal sulfonate, neutral alkalineearth metal phenate and neutral alkaline earth metal salicylate withexcess alkaline earth metal salt or alkaline earth metal base under thepresence of water; or overbased alkaline earth metal sulfonate,overbased alkaline earth metal phenate and overbased alkaline earthmetal salicylate obtained by reacting neutral alkaline earth metalsulfonate, neutral alkaline earth metal phenate and neutral alkalineearth metal salicylate with carbonate or borate of alkaline earth metalunder the presence of carbon dioxide gas.

In the present invention, the content of the alkaline earth metal-baseddetergent is 0.35 mass % or less in terms of alkyl earth metal,preferably 0.01 to 0.35 mass %, more preferably 0.1 to 0.35 mass %. Whenthe content of the alkaline earth metal-based detergent is 0.01 mass %or more, the lubricating oil composition exhibits more excellentoxidation stability, base-number retention and high-temperaturedetergency. On the other hand, when the content of the alkaline earthmetal-based detergent exceeds 0.35 mass %, performance of catalyst forpurifying exhaust gas may be deteriorated. In addition, when such adetergent is used in a diesel engine with a DPF, an amount of ashcontent adhering to the DPF may be increased, thereby shorting the lifeof the DPF.

The lubricating oil composition according to the present inventionpreferably contains a phenol-based antioxidant and/or an amine-basedantioxidant as the antioxidant.

Examples of the phenol-based antioxidant are:octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;4,4′-methylenebis(2,6-di-t-butylphenol); 4,4′-bis(2,6-di-t-butylphenol);4,4′-bis(2-methyl-6-t-butylphenol);2,2′-methylenebis(4-ethyl-6-t-butylphenol);2,2′-methylenebis(4-methyl-6-t-butylphenol);4,4′-butylidenebis(3-methyl-6-t-butylphenol);4,4′-isopropylidenebis(2,6-di-t-butylphenol);2,2′-methylenebis(4-methyl-6-nonylphenol);2,2′-isobutylidenebis(4,6-dimethylphenol);2,2′-methylenebis(4-methyl-6-cyclohexylphenol);2,6-di-t-butyl-4-methylphenol; 2,6-di-t-butyl-4-ethylphenol;2,4-dimethyl-6-t-butylphenol; 2,6-di-t-amyl-p-cresol;2,6-di-t-butyl-4-(N,N′-dimethylaminomethylphenol);4,4′-thiobis(2-methyl-6-t-butylphenol);4,4′-thiobis(3-methyl-6-t-butylphenol);2,2′-thiobis(4-methyl-6-t-butylphenol);bis(3-methyl-4-hydroxy-5-t-butylbenzyl)sulfide;bis(3,5-di-t-butyl-4-hydroxybenzyl)sulfide;n-octyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate;n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl)propionate;2,2′-thio[diethyl-bis-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] andthe like. Among the above, bisphenyl-based antioxidant and estergroup-containing phenol-based antioxidant are preferable.

Examples of the amine-based antioxidant are: an antioxidant based onmonoalkyldiphenylamine such as monooctyldiphenylamine andmonononyldiphenylamine; an antioxidant based on dialkyl diphenylaminesuch as 4,4′-dibutyldiphenylamine, 4,4′-dipentyldiphenylamine,4,4′-dihexyldiphenylamine, 4,4′-diheptyldiphenylamine,4,4′-dioctyldiphenylamine and 4,4′-dinonyldiphenylamine; an antioxidantbased on polyalkyldiphenylamine such as tetrabutyldiphenylamine,tetrahexyldiphenylamine, tetraoctyldiphenylamine andtetranonyldiphenylamine; and an antioxidant based on naphthylamine,specifically alkyl-substituted phenyl-α-napthylamine such asα-naphthylamine, phenyl-α-naphthylamine, butylphenyl-α-naphthylamine,pentylphenyl-α-naphthylamine, hexylphenyl-α-naphthylamine,heptylphenyl-α-naphthylamine, octylphenyl-α-naphthyl amine andnonylphenyl-α-naphthylamine. Among the above, a dialkyldiphenylamine-based antioxidant and a naphthylamine-based antioxidantare preferable.

As another antioxidant, a molybdenum-amine complex-based antioxidant maybe used. As the molybdenum-amine complex-based antioxidant, a hexahydricmolybdenum compound, an example of which is a reaction product obtainedby reacting molybdenum trioxide and/or molybdenum acid with an aminecompound, may be used. The reaction product may be, for example, acompound obtained by the manufacturing method disclosed inJP-A-2003-252887. The anime compound to be reacted with the hexahydricmolybdenum compound subjects to no particular limitation, and examplesthereof are monoamine, diamine, polyamine and alkanolamine. Specificexamples of the amine compound are: alkyl amine having an alkyl group of1 to 30 carbon atoms (the alkyl group may contain a linear chain or abranched chain), exemplified by methylamine, ethylamine, dimethylamine,diethylamine, methylethylamine, methylpropylamine and the like; alkenylamine having an alkenyl group of 2 to 30 carbon atoms (the alkenyl groupmay contain a linear chain or a branched chain), exemplified byethenylamine, propenylamine, butenylamine, octenylamine and oleylamine;alkanol amine having an alkanol group of 1 to 30 carbon atoms (thealkanol group may contain a linear chain or a branched chain),exemplified by methanolamine, ethanolamine, methanolethanolamine andmethanolpropanolamine; alkylenediamine having an alkylene group of 1 to30 carbon atoms, exemplified by methylenediamine, ethylenediamine,propylenediamine and butylenediamine; polyamine such asdiethylenetriamine, triethylenetetramine, tetraethylenepentamine andpentaethylenehexamine; a heterocyclic compound obtained by reactingmonoamine, diamine and polyamine with a compound having an alkyl oralkenyl group of 8 to 20 carbon atoms or imidazoline, monoamine, diamineand polyamine being exemplified by undecyldiethylamine,undecyldiethanolamine, dodecyldipropanolamine, oleyldiethanolamine,oleylpropylenediamine and stearyltetraethylenepentamine; analkylene-oxide adduct of the compounds; and a mixture thereof. Inaddition, sulfur-containing molybdenum complexes of succinimide asdisclosed in JP-B-03-22438 and JP-A-2004-2866 may be used.

A content of the antioxidant is preferably 0.3 mass % or more of thetotal amount of the composition, more preferably 0.5 mass % or more. Onthe other hand, when the content exceeds 2 mass %, the antioxidant maynot be dissolved in the base oil of the lubricating oil. Accordingly,the contents of the antioxidant is preferably in a range from 0.3 to 2mass % of the total amount of the composition.

The lubricating oil composition according to the present invention maybe added as necessary with other additives such as a viscosity indeximprover, a pour point depressant, antiwear agent, an ashless-typefriction modifier, a rust inhibitor, a metal deactivator, a surfactantand antifoaming agent as long as effects of the present invention arenot hampered.

Examples of the viscosity index improver are polymethacrylate, dispersedpolymethacrylate, an olefin-based copolymer (such as anethylene-propylene copolymer), a dispersed olefin-based copolymer, astyrene-based copolymer (such as a styrene-diene copolymer and astyrene-isoprene copolymer) and the like. In view of blending effects, acontent of the viscosity index improver is 0.5 to 15 mass % of the totalamount of the composition, preferably 1 to 10 mass %.

An example of the pour point depressant is polymethacrylate having aweight-average molecular weight of 5000 to 50000.

Examples of the antiwear agent are: sulfur-containing compounds such aszinc dithiophosphate, zinc dithiocarbamate, zinc phosphate, disulfides,sulfurized olefins, sulfurized fats and oils, sulfurized esters,thiocarbonates, thiocarbamates (such as Mo-DTC) and the like;phosphorus-containing compounds such as phosphite esters, phosphateesters, phosphonate esters and amino salts or metal salts thereof; and asulfur and phosphorus-containing antiwear agent such as thiophosphiteesters, thiophosphate esters (such as Mo-DTP), thiophosphonate estersand amino salts or metal salts thereof.

As the ashless-type friction modifier, any compounds generally used asthe ashless-type friction modifier for lubricating oil may be used,examples of which are fatty acid, aliphatic alcohol, aliphatic ether,aliphatic ester, aliphatic amine and aliphatic amide that have at leastone alkyl or alkenyl group of 6 to 30 carbon atoms in the molecule.

Examples of the rust inhibitor are petroleum sulfonate, alkylbenzenesulfonate, dinonylnaphthalene sulfonate, alkenyl succinic ester,multivalent alcohol ester and the like. In view of blending effects, acontent of the rust inhibitor is typically 0.01 to 1 mass % of the totalamount of the composition, preferably 0.05 to 0.5 mass %.

Examples of the metal deactivator (copper corrosion inhibitor) arebenzotriazole-based compounds, tolytriazole-based compounds,thiadiazole-based compounds and imidazole-based compounds. Among theabove, the benzotriazole-based compounds are preferable. By adding themetal deactivator, the engine parts can be prevented from beingmetallically corroded and degraded due to oxidation. In view of blendingeffects, a content of the metal deactivator is preferably 0.01 to 0.1mass % of the total amount of the composition, more preferably 0.03 to0.05 mass %.

Examples of the surfactant are nonionic surfactants based onpolyalkylene glycol such as polyoxyethylenealkylether,polyoxyethylenealkylphenylether and polyoxyethylenealkylnaphthylether.

Examples of the antifoaming agent are silicone oil, fluorosilicone oil,fluoroalkylether and the like. In view of a balance between antifoamingeffects and economics, a content of the antifoaming agent is preferablyapproximately 0.005 to 0.1 mass % of the total amount of the compound.

Sulfur content of the lubricating oil composition according to thepresent invention is preferably 0.5 mass % or less of the total amountof the composition, more preferably 0.3 mass % or less, much morepreferably 0.2 mass % or less. When the sulfur content is 0.5 mass % orless, deterioration of the catalyst performance for purifying exhaustgas can be effectively prevented.

Phosphorus content of the lubricating oil composition according to thepresent invention is preferably 0.12 mass % or less of the total amountof the composition, more preferably 0.1 mass % or less. When thephosphorus content is 0.12 mass % or less, deterioration of the catalystperformance for purifying exhaust gas can be effectively prevented.

Sulfated ash content of the lubricating oil composition according to thepresent invention is preferably 1.1 mass % or less, more preferably 1mass % or less. When the sulfated ash content is 1.1 mass % or less,deterioration of the catalyst performance for purifying exhaust gas canbe effectively prevented. In addition, in a case of a diesel engine, theash content accumulated on the filter of the DPF can be reduced, therebypreventing the filter blockage due to the ash content and contributingto a long life of the DPF. The sulfated ash content means ash contentobtained by adding sulfuric acid carbonized residue caused by combustionof samples for heating so that the residue has a constant mass. Thesulfated ash is generally used to know a rough amount of metal-basedadditives contained in the lubricating oil composition. Specifically,the sulfated ash is measured by a method prescribed in “5. ExperimentMethod of Sulfated Ash” of JIS K 2272.

Since the lubricating oil composition according to the present inventioncontains the predetermined amounts of the components (A) and (B), evenwhen used in the internal combustion engine that consumes biofuel, thelubricating oil composition exhibits excellent detergency for the engineparts such as pistons. In addition, when the lubricating oil compositionis combusted, exhaust gas produced by the combustion contains less ashcontent. Accordingly, the lubricating oil composition is favorablyapplicable especially to a diesel engine with DPF.

EXAMPLES

Next, the present invention will be further described in detail based onExamples, which by no means limit the present invention.

Examples 1 to 9 and Comparatives 1 to 3

Lubricating oil compositions containing components shown in Tables 1 and2 respectively were prepared, which were then subjected to such a hottube test as follows. The components used for preparing the lubricatingoil compositions are as follows.

(1) Base Oil of Lubricating Oil: hydrorefined base oil; kinematicviscosity at 40 degrees C. of 21 mm²/s; kinematic viscosity at 100degrees C. of 4.5 mm²/s; viscosity index of 127; % CA of 0.1 or less;sulfur content of less than 20 mass ppm; and NOACK evaporation of 13.3mass %.(2) Polybutenyl Succinic Monoimide A (Component A): number averagemolecular weight of the polybutenyl group being 1000; nitrogen contentof 1.76 mass %; boron content of 2.0 mass %; and B/N of 1.1.

The above polybutenyl succinic monoimide A was manufactured by thefollowing method. 550 g of polybutene (Mn: 980), 1.5 g (0.005 mol) ofcetyl bromide and 59 g (0.6 mol) of maleic acid anhydride were put intoan autoclave of 1 litter, which were then subjected to nitrogensubstitution and reacted with one another at 240 degrees C. for fivehours. After the temperature was lowered to 215 degrees C., unreactedmaleic acid anhydride and unreacted cetyl bromide were distilled awaytherefrom under a low pressure. After the temperature was furtherlowered to 140 degrees C., filtration was conducted. An yield ofobtained polybutenyl succicic anhydride was 550 g and its saponificationnumber was 86 mg KOH/g. 500 g of obtained polybutenyl succicicanhydride, 17.4 g (0.135 mol) of aminoethyl piperazine (AEP), 10.3 g(0.10 mol) of diethylene triamine (DETA), 14.6 g (0.10 mol) oftriethylene tetramine (TETA) and 250 g of mineral oil were put into aseparable flask of 1 litter and reacted with one another in nitrogen gasstream at 150 degrees C. for two hours. After the temperature was raisedto 200 degrees C., unreacted AEP, DETA and TETA and generated water weredistilled away therefrom under a low pressure. An yield of obtainedpolybutenyl succicic imide was 750 g and its base number was 51 mg KOH/g(by a perchloric acid method). 150 g of obtained polybutenyl succicicimide and 20 g of boric acid were put into a separable flask of 500milliliter and reacted with each other in nitrogen gas stream at 150degrees C. for four hours. After generated water was distilled awaytherefrom under a low pressure at 150 degrees C., the temperature waslowered to 140 degrees C. and filtration was conducted. An yield ofgenerated polybutenyl succinic monoimide A was 165 g and its boroncontent was 2.0 mass %. Polyalkylene polyamine having a terminal ringstructure was approximately 40 mol % of the total polyalkylenepolyamine.

(3) Polybutenyl Succinic Bisimide B: number average molecular weight ofthe polybutenyl group being 2000; nitrogen content of 0.99 mass %; andB/N of 0.(4) Polybutenyl Succinic Monoimide C (Component A): number averagemolecular weight of the polybutenyl group being 1000; nitrogen contentof 1.95 mass %; boron content of 0.67 mass %; and B/N of 0.3.

Polybutenyl succicic monoimide C was reacted and manufactured by thesame method as polybutenyl succicic monoimide A, except that 18 g (0.17mol) of diethylene triamine (DETA) and 25 g (0.17 mol) of triethylenetetramine (TETA) were used in place of 17.4 g (0.135 mol) of aminoethylpiperazine (AEP), 10.3 g (0.10 mol) of diethylene triamine (DETA) and14.6 g (0.10 mol) of triethylene tetramine (TETA) and that boric acidwas added by 13 g. An yield of generated polybutenyl succinic monoimideC was 161 g. No polyalkylene polyamine having a terminal ring structurewas contained therein.

(5) Metal-Based Detergent A (Component B): overbased calcium salicylate;base number of 225 mg KOH/g (perchloric acid method); calcium content of7.8 mass %; and sulfur content of 0.3 mass %.(6) Metal-Based Detergent B (Component B): overbased calcium phenate;base number of 255 mg KOH/g (perchloric acid method); calcium content of9.3 mass %; and sulfur content of 3.0 mass %.(7) Metal-Based Detergent C (Component B): calcium sulfonate; basenumber of 17 mg KOH/g (perchloric acid method); calcium content of 2.4mass %; and sulfur content of 2.8 mass %.(8) Phenol-Based Antioxidant:octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.(9) Amine-Based Antioxidant: dialkyl diphenylamine; nitrogen content of4.62 mass %.(10) Viscosity Index Improver: olefin copolymer; mass average molecularweight of 90000; and resin content of 11.1 mass %.(11) Pour Point Depressant: polymethacrylate; and mass average molecularweight of 6000.(12) Zinc Dialkyl Dithio Phosphate: Zn content of 9.0 mass %; phosphoruscontent of 8.2 mass %; sulfur content of 17.1 mass %; and the alkylgroup being a mixture of a secondary butyl group and a secondary hexylgroup.(13) Copper Corrosion Inhibitor:1-[N,N-bis(2-ethylhexyl)aminomethyl]methyl benzotriazole.(14) Other Additives: a rust inhibitor, a surfactant and an antifoamingagent.

Measurement of properties of the lubricating oil compositions and thehot tube test were conducted in the following manner.

(Calcium Content)

Measurement was conducted based on JIS-5S-38-92.

(Boron Content)

Measurement was conducted based on JIS-5S-38-92.

(Nitrogen Content)

Measurement was conducted based on JIS K2609.

(Phosphorus Content)

Measurement was conducted based on JPI-5S-38-92.

(Sulfur Content)

Measurement was conducted based on JIS K2541.

(Sulfated Ash Content)

Measurement was conducted based on JIS K2272.

(Hot Tube Test)

As the lubricating oil composition to be tested, mixed oil in whichbiofuel (fuel obtained by transesterifying canola oil with methylalcohol) was mixed by 5 mass % of each of the lubricating oilcompositions (new oil) was used, assuming a mixing ratio of the fuel andthe lubricating oil in an internal combustion engine. The measurementwas conducted with the test temperature being set at 280 degrees C. andother conditions being based on JPI-55-55-99. For reference, the sametest was also conducted using only new oil. In addition, since the hottube test may be affected by the amount of the viscosity index improver,the mixing amount of the viscosity index improver was made constantamong Examples and Comparatives. The smaller an amount of fouling on theglass tube after the test was, the more favorable the detergency is.

The properties of the lubricating oil compositions and the results ofthe hot tube test are shown in Tables 1 and 2.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Contained Base Oil of Lubricating Oil 82.11 82.11 81.61 80.61 79.9283.14 Components Polybutenyl Succinic Monoimide 1.00 1.00 1.00 2.00 3.001.00 (mass %) A (B/N = 1.1) Polybutenyl Succinic Bisimide 5.00 5.00 5.005.00 5.00 5.00 B (B/N = 0) Polybutenyl Succinic Monoimide — — — — — — C(B/N = 0.3) Metal-Based Detergent A 2.82 2.82 2.82 2.82 2.82 —Metal-Based Detergent B — — — — — 1.00 Metal-Based Detergent C — — — — —0.60 Phenol-Based Antioxidant 0.50 — 0.50 0.50 0.50 0.50 Amine-BasedAntioxidant — 0.50 0.50 0.50 0.50 0.50 Viscosity Index Improver 6.506.50 6.50 6.50 6.50 6.50 Pour Point Depressant 0.30 0.30 0.30 0.30 0.300.30 Zinc Dialkyl Dithio Phosphate 1.22 1.22 1.22 1.22 0.91 0.91 CopperCorrosion Inhibitor 0.05 0.05 0.05 0.05 0.05 0.05 Others 0.50 0.50 0.500.50 0.50 0.50 Total 100.00 100.00 100.00 100.00 100.00 100.00Composition Calcium Content 0.22 0.22 0.22 0.22 0.22 0.11 PropertiesBoron Content 0.02 0.02 0.02 0.04 0.06 0.02 (mass %) Nitrogen Content0.07 0.09 0.09 0.11 0.13 0.09 Sulfur Content 0.2 0.2 0.2 0.2 0.2 0.2Phosphorus Content 0.10 0.10 0.10 0.10 0.07 0.07 Sulfated Ash Content0.97 0.97 0.97 0.99 0.94 0.54 Hot Tube 95 mass % New oil plus 5 mass 0.70.5 0.3 0.3 0.2 0.2 Test (Fouling % Biofuel Amount mg) New oil(Reference) 0.3 0.3 0.2 0.1 0.1 0.2

TABLE 2 Example 7 Example 8 Example 9 Comparative 1 Comparative 2Comparative 3 Contained Base Oil of Lubricating Oil 82.64 82.14 82.1482.61 84.14 84.43 Components Polybutenyl Succinic Monoimide 1.00 1.00 —— — 1.00 (mass %) A (B/N = 1.1) Polybutenyl Succinic Bisimide 5.00 5.003.00 5.00 5.00 5.00 B (B/N = 0) Polybutenyl Succinic Monoimide — — 4.00— — — C (B/N = 0.3) Metal-Based Detergent A 0.50 1.00 — 2.82 — —Metal-Based Detergent B 1.00 1.00 1.00 — 1.00 — Metal-Based Detergent C0.60 0.60 0.60 — 0.60 — Phenol-Based Antioxidant 0.50 0.50 0.50 0.500.50 0.50 Amine-Based Antioxidant 0.50 0.50 0.50 0.50 0.50 0.50Viscosity Index Improver 6.50 6.50 6.50 6.50 6.50 6.50 Pour PointDepressant 0.30 0.30 0.30 0.30 0.30 0.30 Zinc Dialkyl Dithio Phosphate0.91 0.91 0.91 1.22 0.91 1.22 Copper Corrosion Inhibitor 0.05 0.05 0.050.05 0.05 0.05 Others 0.50 0.50 0.50 0.50 0.50 0.50 Total 100.00 100.00100.00 100.00 100.00 100.00 Composition Calcium Content 0.15 0.19 0.110.22 0.11 0 Properties Boron Content 0.02 0.02 0.02 0.00 0.00 0.02 (mass%) Nitrogen Content 0.09 0.09 0.11 0.07 0.09 0.07 Sulfur Content 0.2 0.20.2 0.2 0.2 0.2 Phosphorus Content 0.07 0.07 0.07 0.10 0.07 0.10Sulfated Ash Content 0.67 0.80 0.54 0.96 0.53 0.25 Hot Tube 95 mass %New oil plus 5 mass 0.2 0.1 1.5 10.3 15.6 58.1 Test (Fouling % BiofuelAmount mg) New oil (Reference) 0.1 0.1 0.3 0.2 0.3 1.9

[Evaluation Result]

As is understood from the results of the hot tube test shown in Tables 1and 2, Examples 1 to 9, where the lubricating oil composition accordingto the present invention was used, produced almost as small an amount offouling as the new oil (i.e., a lubricating oil composition to which nobiofuel was added), irrespective of the addition of the biofuel. Incontrast, Comparatives 1 and 2, where the component (A) according to thepresent invention was not contained, produced a much larger amount offouling than the new oil, thereby exhibiting inferior detergency for theengine. In addition, Comparative 3, where the component (B) according tothe present invention was not contained, produced a much larger amountof fouling than the new oil as did Comparatives 1 and 2, therebyexhibiting inferior detergency for the engine.

INDUSTRIAL APPLICABILITY

The lubricating oil composition according to the present invention isfavorably applicable to an internal combustion engine in which biofuelor fuel mixed with the biofuel is employed.

1. A lubricating oil composition for an internal combustion engine, theinternal combustion engine using a fuel that comprises at least one fatand oil selected from a group consisting of natural fat and oil,hydrotreated natural fat and oil, transesterified natural fat and oiland hydrotreated transesterified natural fat and oil, wherein thelubricating oil composition comprises: a base oil of lubricating oil; acomponent (A) comprising a boron derivative of a succinimide compoundsubstituted by an alkyl or alkenyl group having a number averagemolecular weight of 200 to 5000; and a component (B) comprising analkaline earth metal-based detergent, and wherein the lubricating oilcomposition comprises the component (A) of 0.01 to 0.2 mass % in termsof boron of a total amount of the composition and the component (B) of0.35 mass % or less in terms of the alkaline earth metal of the totalamount of the composition.
 2. The lubricant oil composition according toclaim 1, wherein a mass ratio (B/N) of boron (B) and nitrogen (N) in thecomponent (A) is 0.5 or more.
 3. The lubricant oil composition accordingto claim 1, wherein the lubricating oil composition comprises at leastone of a phenol-based antioxidant and an amine-based antioxidant in anamount of 0.3 mass % or more of the total amount of the composition. 4.The lubricant oil composition according to claim 1, wherein a sulfurcontent is 0.5 mass % or less of the total amount of the composition. 5.The lubricant oil composition according to claim 1, wherein a phosphoruscontent is 0.12 mass % or less of the total amount of the composition.6. The lubricant oil composition according to claim 1, wherein asulfated ash content is 1.1 mass % or less.
 7. The lubricant oilcomposition according to claim 3, wherein a sulfur content is 0.5 mass %or less of the total amount of the composition.
 8. The lubricant oilcomposition according to claim 3, wherein a phosphorus content is 0.12mass % or less of the total amount of the composition.
 9. The lubricantoil composition according to claim 4, wherein a phosphorus content is0.12 mass % or less of the total amount of the composition.
 10. Thelubricant oil composition according to claim 7, wherein a phosphoruscontent is 0.12 mass % or less of the total amount of the composition.11. The lubricant oil composition according to claim 3, wherein asulfated ash content is 1.1 mass % or less.
 12. The lubricant oilcomposition according to claim 4, wherein a sulfated ash content is 1.1mass % or less.
 13. The lubricant oil composition according to claim 5,wherein a sulfated ash content is 1.1 mass % or less.
 14. The lubricantoil composition according to claim 7, wherein a sulfated ash content is1.1 mass % or less.
 15. The lubricant oil composition according to claim8, wherein a sulfated ash content is 1.1 mass % or less.
 16. Thelubricant oil composition according to claim 9, wherein a sulfated ashcontent is 1.1 mass % or less.
 17. The lubricant oil compositionaccording to claim 10, wherein a sulfated ash content is 1.1 mass % orless.